Pinch valves are often used on medical devices to noninvasively close clear plastic flexible tubes carrying blood or other liquids. The tube is pinched between a movable nose driven by a linear or rotary solenoid and a fixed member. A linear solenoid can be arranged to pinch the tube when the solenoid is powered and to open the tube (through resiliency of the tube or a spring return) when the solenoid is not powered; this type of arrangement has been used to repeatedly open and close (e.g. a couple of times a minute) blood tubes on single needle control apparatus, e.g., as disclosed in Willock et al. U.S. Pat. No. 4,063,554. A linear solenoid can also be arranged to open the tube when powered and to close the tube using a spring when in the nonpowered state; this type of arrangement has been used as a safety closure mechanism activated on sensing of an air bubble or by a power failure, on two needle dialysis machines. When using a spring-to-close arrangement, large amounts of energy are required to set the spring, and it is noisy when it snaps shut.